Geophysical investigation of the pressure field produced by water guns at a pond site in La Crosse, Wisconsin

Abstract

Three different geophysical sensor types were used to characterize the underwater pressure waves generated by the underwater firing of a seismic water gun and their suitability for establishing a pressure barrier to potentially direct or prevent the movement of the Asian carps. The sensors used to collect the seismic information were blast rated hydrophones and underwater blast sensors. Specific location information for the water guns and the sensors was obtained using either laser rangefinders or differentially corrected global positioning systems (GPS). Two separate studies are discussed in this report. The two studies were completed during September 2012 and July 2013. Both of these studies took place in an earthen testing pond on the campus of Upper Midwest Environmental Sciences Center (UMESC) in La Crosse, Wisconsin. Previous studies had identified 5 pounds per square inch (lb/in 2 ) as a target value for the successful operation of a water gun barrier. The September 2012 study evaluated the performance of 1-cubic-inch (in 3) and 80-in 3 water guns. Data from the 1-in 3 gun showed that it produces a very planar wave with limited effect on the depths above and below its gun ports. The 1-in 3 gun did not produce the 5-lb/in 2 target pressure at a sufficient distance to be considered effective. The 80-in 3 gun produced a bowl-shaped pressure field with the 5-lb/in 2 target radius at the surface extending to 45 feet. The July 2013 study consisted of three scenarios: fish behavior, single gun assessment, and experimental barrier evaluation. The fish behavior scenario simulated the pond conditions from previous studies. Two 80-in 3 water guns were fired in the south end of the testing pond. Pressures essentially doubled from the testing of the single 80-in 3 water gun. The single gun assessment scenario sought to replicate the setup of the 80-in 3 scenario in September 2012, but with additional sensors to better define the pressure field. The 5-lb/in 2 target pressure field continued to show a radius ranging from 40 to 45 feet, dependent on the pressure of the input air. The final scenario, the experimental barrier evaluation, showed that a two-dimensional continuous plane of 5 lb/in 2 can be created between two 80-in 3 water guns to a separation of 99 feet and a depth of 6.5 feet with 1,500 lb/in 2 of input air.